The present invention relates to improved urethane-type polymer producing compositions. More particularly, the present invention relates to improved storage stable polymer-producing compositions comprised of one or more compounds having reactive hydrogen atoms, one or more cyclic nitrile compounds and a catalyst comprising a halide of a metal from Group IIb of the Periodic Table.
In the past, it has been common practice to prepare ureas, urethanes, and thiourethanes by the reaction of an isocyanate and an active hydrogen-containing material. Although the use of isocyanates for the preparation of ureas, urethanes, and thiourethanes is quite popular and extensively employed, there are a number of problems with this reaction. First, the isocyanates are unstable and present storage and handling difficulties. Secondly, many isocyanates, particularly the aliphatic isocyanates, are highly toxic. Thirdly, the reactivity of the --NCO group precludes premixing of the isocyanate with the reactive hydrogen-containing material to form a single component system without first blocking the terminal isocyanate groups. However, curing the blocked isocyanate materials to liberate the blocking group and to reactivate the --NCO group requires high curing temperatures. Finally, in the production of foamed polyurethanes, polythiourethanes, and polyureas, via the isocyanate route, it is necessary to go through the expense and inconvenience of adding a separate foaming agent or of using an excess of isocyanate and water to obtain the required gas release.
The disadvantages mentioned above are not, however, present in a process for preparing polymeric organic compounds by condensation of a compound containing a reactive hydrogen with a compound having the structural formula: ##EQU2## wherein X is carbonyl, thionyl or oxalyl, R is an organic radical free of reactive hydrogen atoms, and n is 2 or more.
There are several known techniques for carrying out the reaction of an active hydrogen-containing material with cyclic nitrile compounds in the presence of catalysts. For example, in U.S. Pat. No. 3,531,425 a process is described in which the reaction is carried out in the presence of a strong base such as tertiary amines, having a pKa above 8. In U.S. Pat. No. 3,652,507 the reaction is carried out in the presence of soluble catalysts containing a first metal from Groups III through V of the Periodic System and a second metal from Groups I, II or the iron series of Group VIII of the Periodic System. It was found in accordance with U.S. Pat. No. 3,625,507 that in most cases strongly basic materials (alkali metal alkoxides, tertiary amines, etc.) must be utilized in conjunction with the catalysts in order to obtain reaction rates which are acceptable for foam formulation. In U.S. Pat. No. 3,702,320 it is disclosed that the reaction may be carried out in the presence of a soluble compound of aluminum, tin, titanium, zinc, bismuth or iron at a temperature of about 120.degree.C to 150.degree.C, provided that when the metal is aluminum, tin, titanium, or bismuth no metal of Group I, II or the iron series of Group VIII is present and when the metal is zinc or iron, the reaction is conducted in the absence of metals of Groups III through V.
Copending U.S. patent application Ser. No. 427,153, filed on Dec. 21, l973 in the name of L. G. Wolgemuth discloses that the reactions may be carried out in the presence of an alkali metal salt of an organic acid and a metal ion of Groups III through V of the Periodic Table.
The catalyst systems described in U.S. Pat. No. 3,652,507 are effective in catalyzing the condensation-rearrangement reaction but they have disadvantages which detract from their desirability. First, they are difficult to prepare and their preparation involves several chemical steps including a purification step. Secondly, they have relatively poor storage stability and, therefore, should be freshly prepared for greatest effectiveness. Thirdly, polymer prepared using the described catalyst systems often undergoes thermal degradation upon further processing. Urethane-type polymer producing compositions made from the above described catalytic systems having relatively poor shelf life. Because of the need for storage stable urethane-type polymer producing systems new and improved catalyst systems and compositions are continuously sought.
It is, therefore, an object of the present invention to present storage stable compositions which react upon heating to produce compounds having two or more urea, urethane or thiourethane groups comprised of a cyclic nitrile compound, and an organic compound having active hydrogens. Another object of the present invention is to present improved polyurethane-type polymer producing compositions in dry powdered form which can be reacted to produce compounds having two or more urea, urethane or thiourethane groups comprised of cyclic nitrile compounds, organic compounds having active hydrogen atoms and an anhydrous catalyst. It is another object of the invention of present improved urethane-type polymer producing compositions which react to produce polymers having improved thermal stability.
These and other objects and advantages of the present invention will be apparent from the following detailed description.